Spreadsheet version
An always up-to-date spreadsheet with composition, heat treatments, and mechanical properties can be obatined HERE.
API 6ACRA Chemical Composition
This is UNS N07718 chemical composition as per the American Petroleum Institute (API) 6ACRA standard.[1]
| Element | Wt% |
|---|---|
| Ni | 50.0 –55.0 |
| Cr | 17.0 – 21.0 |
| Mo | 2.80 – 3.30 |
| W | — |
| Fe | balance |
| Nb | — |
| Nb + Ta | 4.87 – 5.20 |
| Ti | 0.80 – 1.15 |
| Al | 0.40 – 0.60 |
| C | 0.045 max. |
| Mn | 0.35 max. |
| Co | 1.00 max. |
| Cu | 0.23 max. |
| Si | 0.35 max. |
| P | 0.010 max. |
| S | 0.010 max. |
| B | 0.060 max. |
| Pb | 0.0010 max. |
| Ca | 0.0030 max. |
| Mg | 0.0060 max. |
| PREN (PREN, W) | 26.24–31.89 (26.24–31.89) |
Where:
$$ {\text{PRE}_{\text{N}}} = {{\text{wt%Cr}}} + 3.3 \cdot {\text{wt%Mo}} + 16 {\text{wt%N}} $$
$$ {\text{PRE}_{\text{N, W}}} = {{\text{wt%Cr}}} + 3.3 \cdot \left( {{{\text{wt%Mo}}} + 0.5 {\text{wt%W}}} \right) + 16 {\text{wt%N}} $$
More information
Heat treatment requirements and mechanical properties can be consulted here.
Reference
-
API 6ACRA, “Age-hardened Nickel-based Alloys for Oil and Gas Drilling and Production Equipment” (Houston, TX: American Petroleum Institute, 2015).↩
